Reserves of fossil diesel and petroleum distillates are running out. Biodiesel is an alternative fuel source. Biodiesels include alkyl esters. The alkyl esters may be produced by the transesterification of fatty acids contained in a biodiesel feedstock.
Biodiesel feedstocks can be obtained from animal, plant or algae sources. Animal sources include fats such as tallow, lard, and yellow grease. Currently it is not economically feasible to use animal sources as biodiesel feedstocks for biodiesel production on a commercial scale. In any case, the supply of animal sources cannot meet the current demand for biodiesel feedstock.
Plant sources include soybean, rapeseed and palm oil. They also include waste products such as may be obtained from the use of these oils, for example from food manufacturing and processing industries and from hospitality industry, including restaurants and the like. Ultimately the infrastructure and production costs for producing biodiesel from plant sources are far greater than the costs for producing diesel from fossil reserves or petroleum distillates.
Algae have also been investigated as a source of fatty acid for a biodiesel feedstock. However, the “Aquatic Species Program”, a research program on the use of algae for production of biodiesel which was conducted by the US National Renewable Energy Laboratory from 1978 to 1996 found that commercial production would require an algal strain having a capacity for fast growth rate and high lipid content. Such strains were found to be either very difficult to isolate or very difficult to culture on a commercial scale to provide an acceptable yield of fatty acids.